The present invention relates to substituted 3,4-dimethylenedioxythiophenes which can be made by effecting reaction between a 2,5-carbalkoxy-3,4-dihydroxythiophene and an epihalohydrin. More particularly the present invention relates to polymeric substituted 3,4-polymethylenedioxythiophenes which can be used for EMI shielding, smart windows and switches.
Prior to the present invention, as shown by European Patent 0339340, poly(3,4-dialkoxythiophenes) having the formula, ##STR1## were provided useful as anti-static materials, where A is a C.sub.1 -C.sub.4 alkylene radical, a cyclohexyl radical or a phenyl substituted ethylene radical. There was also discussed by Mercouri G. Kanatzidis, in the Dec. 3, 1990, Special Report on Conductive Polymers on pages 36-54 of the Chemical And Engineering News, incorporated herein by reference, that polythiophenes were useful in making electrochromic devices. An electrical potential can be applied in the presence of an electrolyte to a polythiophene film applied onto a conductive surface, such as, an SnO.sub.2 coated glass to cause doping and undoping in the conductive polymer. As used hereinafter, the term "doping" means the oxidized state or conductive state of an electroactive or electro-optically responsive polymer, while "undoped" means the reduced state or non-conductive state. Other applications of conductive polymers are shown by Wolf et al, U.S. Pat. No. 4,893,908, directed to Adjustable Tint Window With Electrochromic Conductive Polymer. Although considerable progress has been made in the synthesis and investigation of conductive organic polymers, sometimes referred to as "synthetic metals", further effort is needed to discover additional organic polymers having improved conductive and electro-responsive properties.